Leaked files show foreign fighters crossed over into Iraq from Syria, sometimes with the help of Syrian border guards.

An Iraqi border patrol unit in Anbar province came across a group of smugglers – what they were smuggling is unclear – near the Syrian border in May 2009. When they gave pursuit, the Iraqi soldiers found themselves drawn into a gun battle with their western neighbours.

5th division border guards chased some smugglers and exchanged gunfire. The smugglers returned back to Syrian territory and the Syrian forces supported them by using med and light weapons against the 5th division border guards.

In his recently-published memoirs, Tony Blair, the former British prime minister, claimed the Bush administration was close to invading Syria - in part because of its alleged support for the Iraqi militants. The leaked documents contain hundreds of references to Syria's role in Iraq, most of them suggesting a deep involvement with the armed groups.

As with the reports about Iran, an important caveat is in order: these reports only tell one side of the story, and a limited one at that; they lack higher-level analysis, and many of them are based on interviews with informants of often-questionable credibility.

Still, some of the reports are hard to contest, particularly those based on the first-hand observations of US and Iraqi army units. They show Syrian border guards were complicit in the smuggling of weapons and people across the border – and that they at times directly engaged the US and Iraqi forces.

Smuggling operations

Throughout much of the Iraq war, the Bush administration's chief complaint about Syria was that the authorities in Damascus failed to police its borders. That was at the top of the agenda when William Burns, the then-assistant secretary of state for near eastern affairs, travelled to Syria in September 2004 for a lengthy meeting with Bashar al-Assad, the Syrian president. "This visit was driven by one thing and one thing only: Iraq," Imad Moustapha, Syria's ambassador to the United States, said at the time.

Indeed, the WikiLeaks documents describe hundreds of "foreign fighters", including dozens of Syrian citizens, using the country's remote eastern desert as a transit point into Iraq. In June 2005, Iraqi border police engaged a group of men who crossed the border illegally to recover a disabled vehicle – which was "believed to be used in smuggling [operations]." The police came under fire – not from the men recovering the vehicle, but from Syrian border guards.

At 1900D, 3ACR reported SAF on the Syrian/Iraqi border at (38S GA104 336). 1x Syrian truck broke down on the Iraqi border, and Syrian individuals crossed the border to recover the disabled truck. Iraqi border police fired on individuals trying to recover the truck (vehicle was believed to be used in smuggling OPNs). Syrian military dismounts returned fire (SAX, 3x RPG's) at IPB. 1X BRDM was on site, but did not engage. The Syrians recovered the disabled vehicle back into Syria. MTF.

Three years later, in May 2008, a group of militants opened fire on an Iraqi border police unit, kidnapped two officers, and stole one of their vehicles. They later came under fire from Iraqi police while driving the vehicle across the border into Syria; "During the incident, Syrian border guards were also firing on the IBP and allowed the vehicle to enter Syria," a US army report noted.

Some of the reports, though, are hard to believe: A May 2005 cable claims that a Syrian "recruiter" for al-Qaeda in Iraq recently returned to Iraq with "50 Syrian suicide bombers/terrorists". Neither was the information sourced, nor was the report followed by a wave of suicide bombings.

"Rigging... suicide vests"

There are also more serious allegations in the leaked documents: that Syrian soldiers fired on their Iraqi counterparts to help smugglers cross the border, and that Syrian intelligence officers helped militants develop new bomb-making techniques. But these reports are often poorly-sourced, and their accuracy is hard to gauge.

In November 2006, for example, an intelligence report on a new wave of planned suicide bombings blamed the Syrian (and Iranian) government for helping to orchestrate them.

Syrian intelligence has been rigging surplus US military uniforms, to include winter coats, as suicide vest improvised explosive devices (SVIED). These uniforms are destined to be used in Iraq, no further information (NFI).

The source of the information is not identified, though. US forces also do not try to assess the validity of the information. Still, the use of suicide vests did become an increasingly popular tactic for al-Qaeda in Iraq in late 2006 and 2007; by early 2008, the US military was calling it the group's "favoured tactic".

A similar report describes Iraqi border patrol officers detaining a group of alleged insurgents:

After tactical questioning by the IBDF, the individuals claimed to be from various Syrian defence forces, ranging from Syrian army conscripts to Syrian border police. The 4X UIM were not in uniform and produced only CIV ID.

But, as the report notes, the men did not carry any Syrian military identification, and there is no follow-up reporting on the incident.